Hydrogen Induced Cracking
Hydrogen-induced corrosion: atomic hydrogen is absorbed into the metal lattice, leading to blistering and embrittlement. This reduces toughness and increases crack risk.
Physicochemical Mechanism of Action
Hydrogen-induced cracking (HIC) occurs when atomic hydrogen gets trapped in the metal lattice. This happens during corrosion reactions when hydrogen is absorbed from the surrounding medium and held in the lattice.
Metallurgical Relevance & Welding Risks
Hydrogen pickup leads to internal blistering or embrittlement of the metal. This severely reduces toughness and increases crack risk, especially under high mechanical loads. HIC can also cause visible loss of strength and make the material crack unexpectedly.
Workshop Practice & Action Guidelines
To avoid or minimize HIC, it's important:
• Cool the weld as quickly as possible to lower the hydrogen pressure in the lattice.
• For hardenable steels (like martensitic), do a careful post-weld treatment, e.g., austenitizing or tempering.
• Choose welding parameters (voltage, speed) to keep embrittlement minimal.
• For special applications, hydrogen removal by hydrogen release or cold treatment may be required.